This package demonstrates how lexical scopes could be implemented to Swift Syntax. After running, it prints declaration each DeclReferenceExprSyntax refers to in the input source code. Right now, the implementation works with:

• Variable declarations (VariableDeclSyntax)
• If expression optional bindings (OptionalBindingConditionSyntax)
• Function parameters (FunctionParameterSyntax)

The main goal of this implementation is to modularize the API for easier future maintainance and adding potential new scopes. Some inspiration was taken from the C++ implementation of scopes.

Simply clone the repository and run the swift package with swift run command or Xcode. The console should print for each reference it's declaration. To change the input code, adjust the content variable in the main() function of the Parse class.

This demo allows for looking up declarations of variables referenced in DeclReferenceExprSyntax and scopes of the references through two new properties: declaration and parentScope. In this demo, CodeBlockSyntax got extended with one additional property scope of type BlockScope. It contains all information about the variables available and introduced in the scope. Additionally there's GlobalScope associated with SourceFileSyntax.

Represents a declaration in the source code. Serves as an abstraction over Syntax for easier name lookup. It consists of three properties and two methods:

• syntax - holding the AST syntax representation of the declaration.
• names - containing all identifiers of the declaration.
• position - holding the AbsolutePosition of the syntax
• refersTo(name:) - checking if passed name refers to one of the declarations within the syntax
• refersTo(names:) - checking whether one of the passed names refers to one of the names within the syntax

It's a general abstraction of any scope available in swift language. Each scope has:

• parent - parent scope of the scope.
• introducedVariables - is a class that should be overriden after subclassing. Returns all variable declarations introduced by the scope like e.g. function parameters, optional bindings, newValue in a getter etc. Used for determining variable shadowing.
• getAllDecl(before:) - returns all declarations available before specified AbsolutePosition.
• getDecl(of:) - returns the declaration a specified DeclReferenceExprSyntax refers to.

It's always the root of the scope tree. Represented and associated in the AST by SourceFileSyntax. Implements the scope protocol. It doesn't have any additional properties.

Represents the scope within brackets where order of the declarations matters. Represented and associated in the AST by CodeBlockSyntax. Should be subclassed before use. It has several additional properties and methods:

• startDeclarations - contains all declarations passed from the parent scope.
• localDeclarations - contains all declarations in the represented scope.

Are example implementation of BlockScope protocol. They both fill in introducedVariables with the variables introduced by the scope.

On top of this foundation, it should be fairly straight forward to implement new scope types. Doing such would require:

1. Subclassing BlockScope
2. Filling in introducedVariables accrodingly
3. Updating scope computed property of CodeBlockSyntax